docs: def _status_filter_to_query(clause):
          """
          Convert a clause querying for an experiment state RUNNING or DEAD.
  
          Queries that check for experiment state RUNNING and DEAD need to be
          replaced by the logic that decides these two states as both of them
          are stored in the Mongo Database as "RUNNING". We use querying by last
          heartbeat time.
  
          :param clause: A clause whose field is "status" and "value" is one of
          RUNNING, DEAD.
          :return: A MongoDB clause.
          """
          if clause["value"] == "RUNNING":
              mongo_clause = MongoRunDAO.RUNNING_NOT_DEAD_CLAUSE
          elif clause["value"] == "DEAD":
              mongo_clause = MongoRunDAO.RUNNING_DEAD_RUN_CLAUSE
          if clause["operator"] == "!=":
              mongo_clause = {"$not": mongo_clause}
          return mongo_clause